Synthesis of four new fluorescent sulfhydryl reagents is described. All are isomers of the previously synthesized N-(iodoacetylaminoethyl)-1-naphthylamine-5-sulfonic acid (1,5-I-AEDANS) and its 1,8-isomer (1,8-I-AEDANS). Three of these new probes (1,4-Br-AEDANS, 2,8-Br-AEDANS, and 2,6-I-AEDANS) carry a single sulfonic acid residue and the fourth (3-(2,7)-Br-AEDANS) carries two sulfonic acid residues. The excitation and emission spectrum of each of these probes is distinct when covalently attached to bovine serum albumin. In addition, they all show a single fluorescent lifetime in the range of 8.0 to 20.8 nsec. This extended range of fluorescent isomers can thus be useful for selecting approprlate energy donors in fluorescence energy transfer experiments.